Isolated pump in a double pass pump Raman oscillator and optimum conversion of pump energy in a Raman oscillator and amplifier

Abstract

A radiation pump recovery system for a double pass pump Raman oscillator is described incorporating a polarizer and quarter waveplate positioned in the optical path of the input pump radiation and functions to separate the reflected pump radiation coming back from the Raman oscillator along the input optical path from said input optical path. In an alternate embodiment the recovery system may include an additional quarter waveplate and mirror to permit unpolarized pump radiation to be separated into two polarizations to drive two Raman oscillators and whereby the reflected pump radiation coming back from the Raman oscillators along the respective input optical paths is separated from said respective input optical path and recombined into a single beam. An alternate embodiment utilizes the rejected pump energy in a Raman amplifier to provide optimal conversion efficiency. The oscillator which may be single pass pump or double pass pump Raman oscillator and amplifier utilize a common Raman active gas in a common housing having windows to provide separate optical paths for the oscillator and amplifier.

I claim: 
     
       1. Apparatus to convert first radiant energy of a first wavelength to second radiant energy of a second wavelength with high conversion efficiency comprising: a Raman oscillator adapted for receiving a beam of said first radiant energy;   said Raman oscillator operated below a predetermined intensity of said first radiant energy to limit unwanted Stokes and Anti-Stokes orders to provide an output of second radiant energy and of unconverted first radiant energy;   a single pass Raman amplifier having an input and output;   first means for coupling said second radiant energy from the output of said Raman oscillator to the input of said Raman amplifier;   second means for delaying said unconverted first radiant energy and for coupling said unconverted first radiant energy to the input of said Raman amplifier to provide an output substantially of second radiant energy;   said Raman oscillator and said single pass Raman amplifier including Raman active gas contained in a common pressure vessel having windows to provide separate optical paths for said Raman oscillator and said Raman amplifier.   
     
     
       2. The apparatus of claim 1 wherein said Raman active gas is methane having at least one hydrogen atom replaced with deuterium. 
     
     
       3. The apparatus of claim 1 wherein said Raman active gas is selected from the group consisting of CD 4 , CH 3  D, CH 2  D 2  and CHD 3  and mixtures thereof.